president obama met mandela just once but says he will forever strive to walk in his footprint. >> i am one of the countless millions who drew inspiration from nelson mandela's life. like so many around the globe, i cannot fully imagine my life without the example mandela set. and so long as i live, i will do what i can to learn from him. >> today we look not only at how mandela is being remembered but also reflect on how his life's mission will be carried forward. >> often when some great man dies, we say we have to wait the judgment of history. i don't think we have to in his case. we start with michelle kosinski. as i understand the crowd has been gathering because the news of madiba's death came so late in the day. explain how you have seen the crowd swell. >> reporter: right. it's just incredible. it has been hundreds upon hundreds of people not stopping for a moment since last night. and people aren't staying all day. they're constantly moving through. so that tells you how many people might have come through here. possibly tens of thousands at this point. and i like that clip